Selenium is a trace mineral required by the body in small amounts. It combines with proteins to make selenoproteins, which are important antioxidant enzymes that may help protect cells from damage by free radicals.
It is thought that selenium may help limit the oxidation of LDL cholesterol, helping to protect against coronary heart disease. Some population studies have linked the antioxidant properties of selenium to lower risk of cardiovascular disease, but the findings are controversial. Selenium deficiency has been implicated in heart disease and other conditions that involve oxidative stress and inflammation, but the evidence is limited.
The selenium content in food depends on the amount of selenium in the soil. Plants can only take up selenium to the extent that it is concentrated in a particular soil. So, if plants are grown in low-selenium soil, they will not provide good dietary sources of selenium.
In the United States, our food supply comes from various regions that are both low and high in selenium. But in some parts of China, for example, the soil is very low in selenium, which may lead to a selenium deficiency there. An often-fatal illness, Keshan's disease (in which the heart muscle is damaged), is frequent among residents living in the low-selenium regions of China.
Some of the richest sources of selenium are fish and whole grains grown in selenium-rich soil. Brazil nuts are especially high in selenium but should be limited to a couple of nuts at a time and eaten only occasionally -- selenium has a very high toxicity if too much is consumed.
Caution must be exercised when taking a selenium supplement, particularly when it is a selenium salt, such as sodium selenite. Organic forms of selenium, such as selenomethionine or selenocysteine, may be less toxic. Currently, there is insufficient evidence to recommend selenium supplements to prevent heart disease.
The jury is still out on whether vitamins and minerals can lower cholesterol. Using the information in this article, you'll know what to expect -- and what not to expect -- from the vitamins in your diet.
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